The present invention generally relates to wideband communication systems using multiplexing modulation techniques. More specifically, the present invention relates to a method of increasing instantaneous or operational bandwidth for digital predistortion linearization in order to compensate for nonlinearities and/or memory effects in multi-channel wideband wireless transmitters.
The linearity and efficiency of radio frequency (RF) power amplifiers (PAs) have become critical design issues for non-constant envelope digital modulation schemes with high peak-to-average power ratio (PAR) values. This has happened as a result of the increased importance of spectral efficiency in wireless communication systems. RF PAs have nonlinearities which generate amplitude modulation-amplitude-modulation (AM-AM) distortion and amplitude modulation-phase modulation (AM-PM) distortion at the output of the PA. These undesired effects may create spectral regrowth in the adjacent channels, as well as in-band distortion which may degrade the error vector magnitude (EVM). Commercial wireless communication systems may for example employ a bandwidth in the range of 20 MHz to 25 MHz. In such an example, these spectral regrowth effects create an undesired impact over a frequency band which is more than 100 MHz to 125 MHz wide. The potential impacts may include inter-system and intra-system interference. Therefore, there is a need in the art for improved methods and systems related to communications systems.